33 research outputs found
Proton Driven Plasma Wakefield Acceleration
Plasma wakefield acceleration, either laser driven or electron-bunch driven,
has been demonstrated to hold great potential. However, it is not obvious how
to scale these approaches to bring particles up to the TeV regime. In this
paper, we discuss the possibility of proton-bunch driven plasma wakefield
acceleration, and show that high energy electron beams could potentially be
produced in a single accelerating stage.Comment: 13 pages, 4 figure
Conformational Basis for Asymmetric Seeding Barrier in Filaments of Three- and Four-Repeat Tau
*S Supporting Information ABSTRACT: Tau pathology in Alzheimer’s disease is intimately linked to the deposition of proteinacious filaments, which akin to infectious prions, have been proposed to spread via seeded conversion. Here we use double electron−electron resonance (DEER) spectroscopy in combination with extensive computational analysis to show that filaments of three- (3R) and four-repeat (4R) tau are conformationally distinct. Distance measurements between spin labels in the third repeat, reveal tau amyloid filaments as ensembles of known β-strand−turn−β-strand U-turn motifs. Whereas filaments seeded with 3R tau are structurally homogeneous, filaments seeded with 4R tau are heterogeneous, composed of at least three distinct conformers. These findings establish a molecular basis for the seeding barrier between different tau isoforms and offer a new powerful approach for investigating the composition and dynamics of amyloid fibril ensembles
The IMiD target CRBN determines HSP90 activity toward transmembrane proteins essential in multiple myeloma
The complex architecture of transmembrane proteins requires quality control (QC) of folding, membrane positioning, and trafficking as prerequisites for cellular homeostasis and intercellular communication. However, it has remained unclear whether transmembrane protein-specific QC hubs exist. Here we identify cereblon (CRBN), the target of immunomodulatory drugs (IMiDs), as a co-chaperone that specifically determines chaperone activity of HSP90 toward transmembrane proteins by means of counteracting AHA1. This function is abrogated by IMiDs, which disrupt the interaction of CRBN with HSP90. Among the multiple transmembrane protein clients of CRBN-AHA1-HSP90 revealed by cell surface proteomics, we identify the amino acid transporter LAT1/CD98hc as a determinant of IMiD activity in multiple myeloma (MM) and present an Anticalin-based CD98hc radiopharmaceutical for MM radio-theranostics. These data establish the CRBN-AHA1-HSP90 axis in the biogenesis of transmembrane proteins, link IMiD activity to tumor metabolism, and nominate CD98hc and LAT1 as attractive diagnostic and therapeutic targets in MM
The ubiquitin proteasome system — Implications for cell cycle control and the targeted treatment of cancer
AbstractTwo families of E3 ubiquitin ligases are prominent in cell cycle regulation and mediate the timely and precise ubiquitin–proteasome-dependent degradation of key cell cycle proteins: the SCF (Skp1/Cul1/F-box protein) complex and the APC/C (anaphase promoting complex or cyclosome). While certain SCF ligases drive cell cycle progression throughout the cell cycle, APC/C (in complex with either of two substrate recruiting proteins: Cdc20 and Cdh1) orchestrates exit from mitosis (APC/CCdc20) and establishes a stable G1 phase (APC/CCdh1). Upon DNA damage or perturbation of the normal cell cycle, both ligases are involved in checkpoint activation. Mechanistic insight into these processes has significantly improved over the last ten years, largely due to a better understanding of APC/C and the functional characterization of multiple F-box proteins, the variable substrate recruiting components of SCF ligases. Here, we review the role of SCF- and APC/C-mediated ubiquitylation in the normal and perturbed cell cycle and discuss potential clinical implications of SCF and APC/C functions. This article is part of a Special Issue entitled: Ubiquitin–Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf
Detection of Chemical Engagement of Solute Carrier Proteins by a Cellular Thermal Shift Assay
Solute
carriers (SLCs) are transmembrane proteins that transport
various nutrients, metabolites, and drugs across cellular membranes.
Despite the relevance of SLCs to cell homeostasis, metabolism, and
disease states, for the majority of SLCs we lack experimental evidence
regarding the nature of the cognate ligands, whether endobiotic or
xenobiotic. Moreover, even for the roughly 20 SLCs for which inhibitors
have been characterized, engagement assays in cells are limited to
the accessibility of radiolabeled or fluorescent probes. The cellular
thermal shift assay (CETSA) has been introduced as a powerful method
to assess target engagement by monitoring ligand-induced changes in
the thermal stability of cellular proteins. We addressed the question
of whether CETSA could be modified to become routinely applicable
to membrane transporters such as SLCs. We used SLC16A1 (MCT1) and
SLC1A2 (EAAT2) as targets to establish robust conditions by which
chemical engagement of SLCs can be detected. Using immunoblotting,
we demonstrate that treatment with the SLC16A1 inhibitors AZD3965
and AR-C155858 stabilized endogenous SLC16A1 in HEK293 cell lysates
as well as intact cells. In addition, the high-affinity ligand of
SLC16A1, l-lactate, and the low-affinity ligand, formate,
resulted in strong and weak stabilization of SLC16A1, respectively.
Moreover, we observed stabilization of SLC1A2 upon treatment with
the selective inhibitor WAY-213613. We propose that the experimental
approach presented here should be generally and easily applicable
for monitoring the engagement of chemical ligands by SLCs in cellular
settings and thus assisting in their deorphanization